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Introduction
(In molecular biology, the enteroviral 3' UTR element is an RNA structure found in the 3' UTR of various enteroviruses.) A UTR, or untranslated region, is a section of mRNA which is not read out in translation and thus does not contribute to the protein sequence. It sequence, and particularly its structure, do have important functions in the cell cycle. (The overall structure forms the origin of replication (OriR) for the initiation of (-) strand RNA synthesis. Pseudoknots have also been predicted in this structure.) These structure are important in virus replication.

Replication
Enteroviruses replicate through the synthesis of a (-) strand RNA from the (+) strand. The newly synthesized strand acts as a template for new (+) strand progeny RNA. While the same proteins are responsible for the synthesis of both strands they recognize two different 3’ elements on the (+) and (-) strands of enterovirus RNA. Proteins recognize oriL on the 3’ end of the (-) strand to initiate synthesis of the (+) strand and oriR on the (+) strand to initiate (-) strand synthesis. The (+) strand 3’ UTR contains two domains X and Y which have hairpin structures. A so-called kissing interaction is formed between the loops of the X and Y domains and is then stacked on the helical portion of the X domain to form the tertiary structure of oriR. An enterovirus subgroup, B-like enteroviruses, contain an additional domain Z.

The 3’ end of the (+) strand also contains a poly(A) tail that interacts with the kissing domain and is essential for replication. The deletion of this tail proves detrimental to the virus. Interestingly, if the kissing interaction is deleted replication will still occur but mutants with a distorted kissing domain exhibit a temperature sensitive or lethal phenotype. The kissing interaction must exhibit wildtype structure or not be present at all, which raises questions as to its function in replication.